Electrical temperature-indicating system



Nov. 11 1947. A. G. CONRAD I. 2,430,756

7 ELECTRICAL TEMPERATURE-INDICATING SYSTEM Filed Nov. 29, 1944 //v|//v70/? I h ALBERT a. CONRAD I ATTORNEYS Patented Nov. 11, 1947 ELECTRICAL TEMPERATURE -INDICATIN G SYSTEM Albert G. Conrad, Mount Carmel, Conn, assignor to Manning, Maxwell & Moore, 1110., Bridgeport, Conn, a corporation of New Jersey Application November 29, 1944, Serial No. 565,732

2 Claims. l

The present invention relates to temperatureindicating systems or apparatus and relates more particularly to systems or apparatus whereby temperatures may be. electrically indicated.

One of the objects of the present invention is to provide a superior system or apparatus of the character referred to, which is characterized b simplicity and reliability in use.

Another object of the present invention is to provide a superior electrical temperature-indieating system or apparatus which will accurately indicate at one station or location, the temperatures existing at another and relatively-remote station or location.

A further object of the present invention is to provide a superior electrical temperature-indicating system or apparatus which will function with accuracy, despite wide variations in the voltages applied thereto.

Other objects will be apparent to those skilled in the art from the following, considered in conjunction with th accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a schematic view of an electrical temperature-indicating system or apparatus embodying the present invention;

Fig. 2 is a diagrammatic view of the electric circuit illustrating the conditions which exist when the temperature in the thermometer-element is such as to cause a balance of forces in the -ratio-meter;'-

Fig. 3 is a view similar to Fig. 2 but illustrating the electrical unbalance of the circuit which occurs when the thermometer-element is subjected to a lower temperature than that affecting the I said element under the. conditions illustrated in gig. is a diagrammatic view of a modified circu The showing of Figs. 1 to 4 inclusive The system or apparatus shown in the figures now under discussion, includes a thermometerelement ill, a balancing-resistor ii, and four armature-shifting coils respectively indicated by the reference characters l2, l3, l4 and I5.

In the instance shown the coils l2, l3, l4 and i5 above referred to, constitute elements of an electrical indicating-instrument of the type commonly referred tons a ratio-meter", and serve to act upon an armature IS in a manner as will more fully hereinafter appear.

As illustrated in Fig. 1, the coils l2, l3, M- and I5 are of rectangular ring-like form, and the said coils are so arranged that the coils I2 and i3 extend parallel with each other in laterally-spacedapart relationship and, similarly, the coils l4 and 15 extend parallel with each other in laterallyspaced-apart relationship. The complemental coils l2 and I3 extend at an angle with respect to the complemental coils l4 and I5, which latter extend through the coils l2 and 13. The armature is before referred to, is so positioned as to be acted upon by the field developed by each of the coils l2, l3, it and I5, and is diametrically arranged with respect to and rigidly mounted upon a shaft or arbor I! which extends in parallelism with the faces of the said coils and is enclosed, so to speak, within the substantiallyrectangular outline provided by th respective centralportions of the four coils l2, l3, l4 and IS.

The upper end of the shaft l! is provided with a rigid radially-extending pointer or indicator l8 which is adaptedto sweep over an arcuate series of graduations l9 printed or otherwise applied to the surfac of a dial-plate 2D. Adjacent each of the ends of the series of indicia l9, the dial-plate 20 is provided with one of two outstanding stop-pins 2| and 22 which are adapted to be engaged by and to limit the movement of the pointer l8. 1

One terminal of the coil I2 is connected by means of a wire 23 to one terminal of the balancing-resistor II, which latter, in turn, has its remaining terminal connected by means of. a wire 24 to one terminal of the thermometer-element l0. Intermediate its respective opposite ends the said wire 24 has connected to it a supply-wire 25 which is complemented by a second supply-wire 26. The said supply-wires 25 and 26 are respectively provided with terminals 21 and .28 to which may be connected any suitable wires leading from a source of A.-C. or D.-C. current of a suitable voltage.

One terminal of the coil I3 is connected by means of a wire 29 to an intermediate portion of the wire 23 which serves to interconnect the coil l2 and the balancing-resistor II, as before described.

The remaining terminal of the coil I2 is con- .3 nected by means of a wire 30 to one terminal of the relatively angularly disposed coll I4. Theopposite terminal of the coil I4 is connected by means of a wire 3| to one temiinal of the thermometer-element III. The opposite terminal of the thermometer-element III is connected by means of the wire 24 before described, to one terminal of the balancing-resistor I I.

The remaining terminal of the coil I3 is connected by means of a wire 32 to one terminal of the relatively angularly disposed (Fig. 1) coil I5, while the remaining terminal of the said coil I5 is connected by means of a wire 33 to the wire 3| which extends between one terminal of the coil I4 and one terminal of the thermometer-element I0.

As before noted, the coils I2, I3, I4 and I5 constitute features of what is commonly referred to as a ratio-meter. In the instance shown, the forces developed at a given instant by the coils I2 and I3 on the one hand, and the forces developed-by the coils l4 and I5 on the other hand, while variable relative to each other are, however, always such as to oppose each other in their respective efiorts to move the armatur I6.

The thermometer-element I may be formed of any suitable material, the resistance of which changes materially with changes in the temperature to which it is subjected. The said thermometer-element may be located at a remote point with respect to the coils I2, I13, I4 and I and associated elements, and may be in the form of a coil formed, for instance, of heat-resistant nichrome.

By reference to Figs. 2, 3 and 4 in particular, it will be seen that the coils I2, I3, I4 and I5, the thermometer-element I0, and the balancingresistor II are electrically arranged in the pattern of a Wheatstone bridge In an electrical sense, though not necessarily in a physical sense, the thermometer-element III, balancing-resistor II, and coils l2 and I I are located in the ringportion of the Wheatstone-bridge pattern, with each thereof located in one of the four arms or sections thereof. and I5 may, for convenience of description, be described as being located in the bridging-portion of the Wheatstone-bridge pattern.

Operation For purposes of description, let it be assumed that the thermometer-element III isso constituted that its resistance increases with a rise in its temperature and vice versa. Let it further be assumed that the resistance of the said thermometer-element I0, when at a temperature of 0 C., will exactly equal the resistance of the balancingresistor I I.

Under the conditions just above referred to, the electrical system will be balanced as indicated by the arrows in Fig. 2, so that the angularly disposed coils I2 and I4 will have equal current-flows therethrough and hence will develop equal and opposite torques on the armature I6 or its equivalent. At this time, due to the balanced condition of the circuit, substantially no current will flow through the coils I3 and I5.

Inasmuch as the armature I6 is subjected to equal and opposite forces by the coils I2 and It respectively, the pointer I8 will assume a midposition with respect to the indicia I9 011' the dial-plate 20. The particular temperature at which the resistance of the thermometer-element III equals the resistance of the balancing-resistor II, may, of course, be made to correspond to any The series-connected coils I3 4 desired point on a thermometer scale by suitably proportioning the thermometer-element I0 and the balancing-resistor I I.

Now let it be assumed that the temperature to which the thermometer-element III is subjected, falls below the arbitrarily-selected temperature of 0 C. at which the electrical system balances. Under the conditions just referred to, the resistance of the thermometer-element Ill will fall with the temperature and hence a greater current will flow therethrough and a lesser current will flow through the balancing-resistor II, as indicated in Fig. 3.

The system will thus become unbalanced and the previously-idle coils I3 and I5 will have a current-flow therethrough to effect their activation, while at the same time the coils I2 and H are energized.

Under the conditions just above referred to, and due to the particular relationships of the coils I2, I3, I4 and I5, the forces developed by the coil I3 will oppose those developed by its complemental coil I2, while at the same time the forces developed by the coil I5 will be such as to aid its complemental coil I4 in deflecting the armature I6. Thus, the net result will be that the armature I6 will be turned in a direction to deflect the pointer I8 toward the low-temperature end of the band of indicia I9. The degree of turning movement of the armature l6 will be in proportion to the unbalance caused in the circuit by the lowering of the resistance of the thermometer-element I0, and hence the indicia I9 may be so arranged as to give direct and accurate indication of the actual temperature to which the thermometer-element I0 is subjected at any given time.

Should the thermometer-element Ill be subject-v ed to a rise in temperature, such as to bring it up above 0 C., the electrical system will become unbalanced in the opposite direction, as indicated in Fig. 4. Under the conditions just referred to, the resistance of the thermometer-element III will increase with the rise in temperature, so that less current will flow therethrough and more of the current will flow through the balancing-retions illustrated in Fig. 3.

Under the unbalanced condition of the circuit as illustrated in Fig. 4, the forces developed by the current-flow through the coil I3 will be added to those developed by the current-flow through the complemental coil I2, while at the same time the forces developed by the current-flow through the coil I5 will be opposed by the forces developed in the coil I4.

Due to the relationship of the forces respectively developed by the coils I2, l3, I4 and I5 as above described, the armature I6 or its equivalent will be turned so as to shift the pointer I8 toward the high-temperature end of the hand of indicia I9. This movement of the armature I6 and. the pointer I8 will be always proportional to the degree of unbalance and hence in accord with the rise in temperature to which the thermometer-element I0 is subjected at any given time.

' The showing of Fig. 5

In the event that it is desired to extend the sweep of the pointer I8, or its equivalent, over a much longer series of indicia such as 19, to thus give more minute indications of temperature changes, the arrangement illustrated in Fig. 5

may be resorted to.

The apparatus illustrated in Fig. 5 correspond to that shown in the preceding figures with the exception that the respective right-ends of the coils l2 and I4, instead of being directly interconnected; are connected respectively through resistors 34 and 35.

The resistor 34 is connected to the Wire 23 which extends between the balancing-resistor I] and the coil l2, by means of a wire 36. The opposite ter-.

with an adjustab1e-o6ntact39 which may be shifted with respect to the resistor 35, to thus adjust the value of the forces developed by the coil I4 with respect to those developed by the complemental coil [5. The end of the resistor 35 opposite the wire 31 is connected by means of a wire 40 to the wire 3!.

General Both forms of the invention shown in the accompanying drawings and herein described, are

- characterized by two pairs of coils so intercon-f nected that the members of the given pair of coils aid each other in turning the armature l6,

while at the same time the members of the other pair of coils are working in opposition to each other except, of course, when the electrical system i balanced as indicated in Fig. 2.

By means of the foregoing arrangement of elements, a simple, reliable and low-cost means is provided for accurately indicating temperatures.

The invention may b carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I claim 1. A temperature-indicating system, including in combination: an indicator; movable armaturemeans operatively connected to the said indicator ,to shift the same; a first pair of stationary armature-shifting coils located adiacent the said armature-means in position to urge the same to movein one direction; a second pair of stationary armature-shifting coils also located adjacent the said armature means in position to move the the same ina direction opposite to that of the said first pair of armature-shifting coils; a2 balancing-resistor; and a thermometer-element; the saidtwo pairs of armature-shifting coils, the said balancing-resistor and the said thermometerelement, being electrically interconnected in a Wheatstone-b'ridge pattern; one of the first Pair 7 of armature-shifting coils and one of the second pair of armature-shifting coils being in series and located in the bridging-portion of the Wheatstone-bridge pattern; the said balancing-resistor and the said thermometer-element. being in the ring-portion of the Wheatstone-bridge pattern on one side of the bridging-portion thereof; and the remaining two armature-shifting coils being located in the ring-portion of the Wheatstonebridge pattern on the side thereof opposite the side in which the said balancing-resistor and thermometer-element are located; the balancingresistor, thermometer-element and two pairs of armature-shifting coils being arranged and proportioned so that when the said thermometerelement is at a predetermined temperature, the bridging;portion of the Wheatstone-bridge. Pattern will have no current flowing therethrough; and when the said thermometer-element has its resistance changed by the lowering of its temperature, the said bridging-portion will have current diverted therethrough in one direction and di-' ture-shifting coils located adjacent the said armature-means in position to urge the same to move.

in one direction; a second pair of stationary armature-shifting coils also located adjacent the said armature-means in position to move the same in a direction opposite to that of the said first pair of armature-shifting coils; a balancing-resistor; and a thermometer-element; the said two pairs of armature-shifting coils, the said balancingresistor and the said thermometer-element being electrically interconnected in a Wheatstonebridge pattern; one of the first pair of armatureshifting coils and one of the second pairof armature-shifting coils being in series and located in the bridging-portion of the Wheatstone-bridge pattern; the'said balancing-resistor and the said thermometer-element being in the ring-portion of the Wheatstone-bridge pattern on one side of the bridging-portion thereof; and the remaining two armature-shifting coils being located in the ring-portion of the Wheatstone-bridge pattern on the side thereof opposite the side in which the said balancing-resistor and thermometer-element are located; and two resistors respectively connected to the two said armature-shifting coils which are in the ring-portion of the Wheatstone- ALBERT G. CONRAD.-

REFERENCES CITED The following references are of record in they file of this patent:

UNITED STATES PATENTS bridge pattern. 

